Maltene fractions: saturates, aromatics and resins

Maltenes:

Maltenes are the n-heptane soluble part of bitumen. They can further be separated into the fractions saturates, aromatics and resins.

Maltenes are a less viscous than bitumen and still black. The structural formation does not occur within pure maltenes, which indicates that asphaltenes play a main part in initialising structural formations, but time dependent effects, like steric hardening, still remain.

The density of maltenes is about 1 g/cm³.

separation of maltenes by chromatographic column separation

Saturates:
Saturates occur at room temperature as a colourless or lightly coloured (white to faint yellow) liquid with a density of about 0,9 g/cm³. With a H/C ratio close to 2 and an average molecular weight of about 600 g/mol saturates are mainly straight and branched-chain aliphatic hydrocarbons with few heteroatoms or aromatic rings. The content of saturates is between 5 to 20wt% for bitumen.

possible molecular saturate structure

Aromatics:
Aromatics or naphthene aromatics appear yellow to orange dissolved from chromatic column and turn to dark red when merged and inspissated with a density about 1 g/cm³. Aromatics are more viscous than saturates and constitute 30 to 60wt% of bitumen. The average molecular weight is 800 g/mol and they compose of lightly condensed aromatic and naphthenic rings with side chains.

possible molecular aromatic structure

Resins:
Resins or polar aromatics are black in solution and inspissated. At room temperature they are solid or semi-solid and liquefy at higher temperature. The density is about 1,07 g/cm³ and resins constitute 15 to 55wt% of bitumen. With similarities between asphaltenes and aromatics there average molecular weight is 1100 g/mol¹ with a wide molecular distribution. The H/C ratio is between 1,38 and 1,69. They consist of 2 to 4 fused aromatic rings and probably with side chains. Resins can be more polar than asphaltenes.

possible molecular resin structure